Ax John Derbyshire 'bout dat.
Posted on 04/08/2012 7:06:52 PM PDT by ConservativeStatement
A Chicago man robbed a Radio Shack of $17,000 in merchandise, but police tracked him down quickly thanks to the global positioning equipment he stole, prosecutors said.
(Excerpt) Read more at chicagotribune.com ...
And he managed to do all this before the age of 21.
In before Grandma says he was such a good boy, and Mama says he was studying to be a heart transplant doctor.
This story stinks.
GPS receivers do not send out any signal. Who would they be sending to?
It’s more likely that there was a GPS locator button on some of the merchandise, sort of like the ones on the top of buses and police cars.
>> “I’m a real amateur when it comes to technology but my cell phone,for example,is capable of broadcasting its location using GPS technology” <<
.
Not quite.
Your cell phone collects data to determine its position from GPS satelites, and then sends the data on the normal cell frequencies. GPS is not a two way communication system. Its a global code phase measurement system.
It sounds as if the correct title should have said. Radio Shack burglarized not robbed. So he probably broke in during the night and made off with a truckload of stuff.
>> “and Mama says he was studying to be a heart transplant doctor.” <<
.
Brain surgeon. Bats and clubs do marvelous brain surgery.
.
LOL
What a maroon!
Take the frickin battry out of a cell phone when house don’t want to be found.
Ax John Derbyshire 'bout dat.
Not according to the article. It says he bound the people at the store with cable ties and stole their cellphones along with other merchandise. That's robbery, not burglary.
It's likely the cellphones were his downfall, not the other merchandise, since any GPS gear in the stolen merchandise would not have been properly activated for tracking (unless maybe he stole display items).
“GPS is receiver not transceiver. So how did they track him?”
Actually I believe it is. I believe that it needs to be able to send a signal to the satellites in order for the whole system to figure out where you are.
Nevermind. I guess that was wrong.
Future fixes happen more quickly with the almanac, rough current location and current time already on board, the receiver knows exactly which "birds" should be visible. It often has 12 concurrent receivers on board. Each one is handed a PN sequence matching a desired satellite. The lockup can be as quick as 15 seconds on a "warm start".
Cell phone get a time stamp off the tower. You get that running start of general location and time. Some can even pass the almanac from the tower. CDMA phones have AGPS. They can leverage the known GPS coordinates of a tower to get a jump start on the positioning calculations or even ask for them to be done as "a service" using precise time offsets to the phone.
Back to the original point. GPS can be done purely passively. No transmissions required. If you have a cell phone, you can leverage the connectivity to save the lag time of the typical GPS cold start. GSM phones can perform a high resolution "ping" using 3 towers to get a pretty decent fix on your with the time offsets. Much of this technology exists per the E911 mandate. It is required to locate any cell phone within 100 meters to support law enforcement 911 services.
Stealing the cell phone was the criminal's mistake.
That would be a monumental scalability problem. Given the rapid expansion of GPS usage, you'd basically have to launch Google into orbit, if the system required client-server interaction with the satellites.
GPS is way cooler than that. GPS is receive-only. It listens to the satellites as they transmit exact times and positions, and it calculates its position by correlating the readings from a minimum of four satellites. Four equations in four unknowns: latitude, longitude, elevation, and time. Actually, it could do with only three satellites, but the fourth is necessary if the GPS receiver lacks its own synchronized, miniaturized, dirt-cheap atomic clock (LOL) — it needs to work out its own time to the nanosecond in order for the concept to work. Additional satellites beyond the minimum of four add to accuracy.
All radio receivers put out a signal, via the first IF. Perhaps they used that to track him. The WWII Germans used the first IF of radio receivers to track people listening to illegal(by German laws)radio broadcasts from the BBC. Remember you can be tracked via your cell phone even when it is turned off, as long as you have the battery in it. You have to remove the battery if you don't wish to be tracked.
Bingo! I called Verizon and asked if there was any unusual traffic on her number and they confirmed it. I explained that the cell phone had gone missing and I suspected it had been stolen. They gave me a list of the recently called numbers. I started working my way down the list.
The fist several were time and temp calls. I got a couple of businesses and at least one confirmed they'd gotten a call about a carpet cleaning appointment. The next was a private residence, After I explained why I was calling, the woman said, “Not this again.”
It turns out her brother-in-law worked for a carpet cleaning company and she gave me the BIL’s name. I called the company and explained the situation to the boss. He was aghast and I told him I'd keep him informed. The next phone number got the employee's home answering machine, so I left a callback number. Then I called the sheriff's office and filed a complaint.
Several hours later I got a call from the BIL. He confirmed that he had the phone, but he maintained that his partner had taken it. I explained that the stupidest thing he'd done was to use the phone because every call he'd made was logged with the time and length of call. Caught, the BIL tried to weasel out. I told him that he'd be visited by the sheriff's office because I'd filed a complaint. I told him that the best thing to do was to turn-in the phone to his boss and he agreed. It was done, I got the phone back, and the BIL was fired.
As part of his plea bargain to avoid jail time, the perp repaid me for the calls made plus my time and effort tracking him down. It took two years but the settlement was the ultimate satisfaction.
I had a credit card stolen from my office. I didn't know it was stolen until two days after the fact. I was already out of town and noticed the missing card. I informed my wife immediately. Hours later, she said my card was recovered in the bushes next to a janitorial business a few miles away. I recalled a goofy call to the front desk the day before I left. I looked at the time stamps of charges to the card. They traced a path from my office through several businesses and ended up in the North Park area of San Diego. I suspected the janitor. I asked security his name. I went to the phone book. He lives on Florida St in North Park. Gotcha! I turned over my detective work to the police department and company security. They set a "trap" and caught him red handed on video stealing a card.
Months passed. This janitor was a 6 ft 2" tall, 220 lb heavily muscled black man. He constantly told tales about his sick girl friend. When I shared that with the detective, he laughed his ass off. Girlfriend? Hell no. All the pretty stuff he bought at the department stores nearby was to dress up for his boyfriend. Ewww!. The guy stole $40,000 total from all the employees on my floor. He was let off with a hand slap. A poor, misunderstood black man. It took me weeks to get all the bad charges on my card resolved.
From my experience with cellphones, I have always been skeptical of this claim, tending to treat it as an urban legend. It implies, of course, that when you turn your phone "off" it's not really turning OFF.
Now, there are certainly appliances with "offs" that are not totally OFF, such as remote controlled TV sets, etc. Another example is my Kindle, which when "off" still runs down the battery using its wireless links to get updates on my digital subscriptions.
But I have not seen any evidence that any cellphone, smart or otherwise, works this way. Admittedly, my personal experience is scarce; I haven't turned any of my cellphones of the last 20 years "off" for a long enough time to see if the battery drains at greater then its self-discharge rate, indicating surreptitious activity.
Anyone have links to definitive info on this? Myrddin? Bueller?
The receiver contains a local oscillator (LO) whose job it is to translate the incoming RF channel to a fixed intermediate frequency (IF) using a device called a mixer. The mixer combines the incoming RF channel with the LO so that the mixer's output is at the intermediate frequency; this is fed to a series of gain stages all fixed-tuned to the IF.
To tune the radio to a given channel, you just vary the LO so that it funnels the right RF channel into the IF section.
The rationale for the superhet architecture is that fixed-tuned gain stages are much, much easier to design than variable-tuned ones.
The most likely radiated energy from a receiver is the LO, which reveals only that the receiver is operating; and, assuming you pick it up and also assume that the receiver uses a commonly selected IF, you can deduce what channel is being received.
The next most likely radiated energy would be the IF signal itself, which does carry the information being received.
However these are both weak signals, effectively undetectable more than a few feet or tens of feet from the receiver in a cellphone.
Considering also how many cellphones would be operating (most of them in standby), it would be like searching for a needle in a haystack.
It is true that there used to be TV rating services that would drive a truck with a sensitive LO receiver and a side-firing directional antenna. It would sweep past the houses and could record which channel each home was tuned to.
By they way, cal, I suspect my pedantic explanation is old news to you; I just wanted to get it on this thread by way of general explanation for the less geeky. If, that is, any of them can stand to read it.
Ed Sullivan....My 45,47 & 49 year old kids don’t know who Ed Sullivan is. They don’t know who Topo Gigio is either. Sa right.
The German Funksicherheitsbedienung was very effective at tracking down covert transmitters. Their motto was Funksendung is Verrat, "Transmission is treason". They tried to impress that on the German Army, with their Enigma machines, but with little success.
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